package day_03;

import java.util.*;

public class SWSecondTest {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        char ret = handle(sc.nextLine());
        System.out.println(ret);
    }

    private static char handle(String str) {
        //HashSet<Character> set = new HashSet<>();
        //LinkedHashSet<Character> set = new LinkedHashSet<>();
        LinkedHashMap<Character, Integer> map = new LinkedHashMap<>();
        char[] array = str.toCharArray();
        for(char ch: array){
            Integer v;
            if(map.containsKey(ch)){
                v = map.get(ch);
                map.put(ch, v + 1);
            }else{
                map.put(ch, 1);
            }
        }

        Set<Character> set = map.keySet();
        for(Character ch: set){
            if(map.get(ch) == 1){
                return ch;
            }
        }
        //Not Exit.
        return ' ';
    }
}
